Field of the Invention
The present invention relates to a rotary table assembly to be set on a machine tool.
Description of the Related Art
In a machine tool such as a machining center, a workpiece to be machined is set on a rotary table and is sometimes subjected to various types of machining such as milling and tapping by means of a tool attached to a spindle. The machine tool comprises a spindle head, vertical movement device, horizontal movement device, and spindle drive device. The spindle head rotatably supports the spindle fitted with the tool. The vertical movement device vertically reciprocates the spindle head, while the horizontal movement device horizontally moves the spindle head. The spindle drive device rotates the spindle. The rotary table that supports the workpiece is enabled to perform more complicated machining by being rotated in accordance with the movement of the spindle.
The machine tool constructed in this manner generally uses a cutting fluid to achieve smooth machining. Further, chips are produced as the workpiece is machined. If the cutting fluid used in the machining or the chips produced during the machining get into the machine tool, the operation of the machine tool may be hindered thereby. As shown in FIG. 8, therefore, a sliding portion of the machine tool is provided with a seal member such that the cutting fluid and chips can be prevented from getting into the machine tool. In FIG. 8, reference numerals 1, 2a and 11 denote a case, shaft, and oil seal, respectively.
Japanese Patent Application Laid-Open No. 2011-104725 discloses a technique in which an air seal ring is disposed between a body and a table rotator of a rotary table, thereby preventing intrusion of foreign matter between the body and the table rotator.
Japanese Patent Application Laid-Open No. 2013-188800 discloses a technique in which a rotating base of a rotating device is grooved to form a labyrinth seal, in order to suppress intrusion of foreign matter into a housing that supports a rotating shaft for rotation.
Japanese Examined Utility Model Application Publication No. 8-112 (JP 8-112, Y2) discloses a technique in which a seal member is disposed between a rotary table bearing and a gap portion of an index table used in a machine tool.
In any of the techniques disclosed in the above three patent documents, intrusion of foreign matter is suppressed by forming a seal structure such as a labyrinth seal between a workpiece mounting table and a fixed portion that constitutes a rotary table. If chips produced during machining are very fine, however, they may adhere to the seal member. If the sliding portion is slid in this state, the seal member may be worn away so that its sealing performance is reduced. Thus, there is a possibility of the cutting fluid and chips getting into the machine tool.
In order to prevent the seal member at the sliding portion from being worn away, therefore, it is essential to protect the seal member. Possibly, moreover, the chips may also adhere to some other portions of the main body of the rotary table than the sliding portion. In this case, removal of the chips during maintenance work is time-consuming, and in addition, the chips may get into the machine tool to cause a further problem when a mechanism section of the machine tool is disassembled during the maintenance work.